1. Field of the Invention
This invention relates to a video signal circuit and more particularly to a video signal circuit having the function of time base correction of video signals.
2. Description of the Prior Art
When video signals recorded on video signal recording media such as video floppy disks or video tapes are reproduced by a reproducing device, so-called jitters or instability along the time axis may be occasionally contained in the reproduced signals usually due to unstable factors peculiar to the recording or reproducing device. When video signals containing jitters are displayed on a video monitor, only unstable images hard to view will be reproduced.
There is also a demand for devices adapted for reproducing an image recorded on a video signal recording medium in the form of a hard copy, that is, for recording it in the form of a visible image on another recording medium such as a sheet of photographic paper. When such a recording device is supplied with video signals containing jitters as video signals to be visualized, it is not possible to produce stable and clear hard copies.
So far, a time base corrector has been used for establishing proper stability in video signals unstable along the time axis, i.e. containing jitters of sync signals. According to a known system of such a time axis corrector, there is provided a video memory for storing video signal data and a sophisticated and complex control is carried out in order to improve stability in time axis, as by controlling read and write timing of video data to the video memory or switching read and write addresses of the memory at the rate of pixel clocks.
On the other hand, large scale integrated circuits (LSI's) have evolved for application of computer terminal devices, which includes on a semiconductor chip a shift register enabling data to be written into and read out of a conventional IC, which is also formed on the chip, serially at a high speed, utilizing the nature of video data signals.